Cabochon gem grinder

ABSTRACT

A cabochon gem grinding machine comprising a drum having a cylindrical wall and a lip extending inwardly from the sides of the wall for retaining a slurry of abrasive grain or grit, a pair of rollers which support and rotate the drum to distribute and maintain the slurry against the inner wall of the drum by centrifugal force, a dop for holding a gem to be ground in contact with the slurry at a desired angle to the vertical to grind a desired area of the gem, a pattern for indicating the desired shape of the gem, and a drive mechanism for rotating the gem and the pattern and for moving them toward a vertical position to grind new areas of the gem. Also, sensing and actuating apparatus is provided for detecting when a gem area has been ground to the desired size and for rotating the gem and pattern and for moving them toward vertical position to grind new areas of the gem. Also, sensing and actuating apparatus is provided for detecting when a gem area has been ground to the desired size and for rotating the gem and pattern and for moving them toward vertical position to grind new areas of the gem. A method of grinding cabochons and the like, comprising maintaining a slurry of abrasive material inside a rotating drum, holding a gem to be ground in contact with the slurry at a desired angle to the vertical to grind a desired area of the gem, rotating the gem and moving it toward the vertical when said gem area has been ground to the desired size, and repeating said steps until the gem has been ground to the desired pattern.

Montgomery et al.

[4 1 May 113, 1975 CABOCHON GEM GRINDER [75] Inventors: Earl D.Montgomery; Jan Michael Montgomery, both of Warrington, Pa.

' [73] Assignee: The American Standard Corporation, Trevose, Pa.

[22] Filed: Dec. 28, 1973 [21] Appl. No.: 429,084

[52] U.S. Cl 51/73 R; 51/283; 51/317 [51] Int. Cl B24b 7/00; B24b 9/00;B24b 1/00 [58] Field of Search 51/73 R, 317, 318,283

[56] References Cited UNITED STATES PATENTS 583,670 6/1897 Chambers etaI. 51/73 R 2,387,138 10/1945 Fruth 51/73 R 2,745,225 5/1956 Vonada t51/73 R 10/1970 Campbell 51/73 R Primary Examiner-Othell M. SimpsonAttorney, Agent, or Firm-Smith, Harding, Earley & Follmer ABSTRACT Acabochon gem grinding machine comprising a drum having a cylindricalwall and a lip extending inwardly from the sides of the wall forretaining a slurry of abrasive grain or grit, a pair of rollers whichsupport and rotate the drum to distribute and maintain the slurryagainst the inner wall of the drum by centrifugal force, a dop forholding a gem to be ground in contact with the slurry at a desired angleto the vertical to grind a desired area of the gem, a pattern forindicating the desired shape of the gem, and a drive mechanism forrotating the gem and the pattern and for moving them toward a verticalposition to grind new areas of the gem. Also, sensing and actuatingapparatus is provided for detecting when a gem area has been ground tothe desired size and for rotating the gem and pattern and for movingthem toward vertical position to grind new areas of the gem. Also,sensing and actuating apparatus is provided for detecting when a gemarea has been ground to the desired size and for rotating the gem andpattern and for moving them toward vertical position to grind new areasof the gem. A method of grinding cabochons and the like, comprisingmaintaining a slurry of abrasive material inside a rotating drum,holding a gem to be ground in contact with the slurry at a desired angleto the vertical to grind a desired area of the gem, rotating the gem andmoving it toward the vertical when said gem area has been ground to thedesired size, and repeating said steps until the gem has been ground tothe desired pattern.

5 Claims, 8 Drawing Figures PATENIEE m a sign; 3, 882.641

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Elsi-32am FATENIEB KAY 3 M5 SEEN 5 PF 5 CABOCHON GEM GRINDER BACKGROUNDOF THE INVENTION The automatic grinding of gem stones to desired shapesand sizes, such as cabochons, is conventionally performed by apositioning device that places a stone in contact with either a grindingwheel or a flat lap charged with diamond powder. The stone is caused tofollow a pattern or template which contacts a wear plate when the stoneis ground down to the desired size to stop further grinding. Such priorart templatecontrolled grinding machines for grinding cabochons ofsemiprecious gems are illustrated by US. Pat. No. 3,568,369 which issuedon Mar. 9, 1971.

Such machines have certain draw-backs. As a stone is abraded by agrinding wheel, the wheel also wears, requiring frequent dressing of thewheel. This dressing causes the surface of the grinding wheel to bepositioned at a greater distance from the stone, so the wear plate mustbe repositioned accordingly to maintain the calibration accuracy of thepattern. Further, diamond laps cut well when new, but become less andless efficient as diamond particles break away from the surface or aredriven into the lap material by the impact of cut- .ting or grinding.Moreover, lap replacement cost is high.

SUMMARY or THE INVENTION Accordingly, it is an object of this inventionto provide an automatic cabochon gem grinding machine which overcomesthe problems of the prior art machines by eliminating the grinding wheeland the flat lap.

This object is accomplished by providing a gem grinder which utilizes aslurry of abrasive grains to grind stones automatically. The abrasivegrains are dispersed and maintained in a lipped drum and maintainedagainst the inner wall of the drum by centrifugal force. The stone isheld against the slurry by a dop which is rotated about its axis inunison with a pattern and is also progressively moved along the wall ofthe drum from an initial angle of about 75 from the vertical to thevertical as the stone is ground in accordance with the pattern.

As the grinding proceeds, material is removed from the abraded area ofthe stone, allowing the pattern to contact a wear or contact plate whichcauses a motor and gearing to turn a worm shaft to rotate both stone andpattern about their axes and about the worm shaft at right anglesthereto to present an uncut area of the stone to the lap. For example,the initial grinding of a stone may start with the dop and pattern axesat 75 from the vertical. As grinding proceeds the dop and pattern axesrotate and also move toward the vertical. When the dop and pattern axisreach the vertical, the gem grinding is complete.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view inperspective of a cabochon gem grinding machine constructed in accordancewith this invention;

FIG. 2 is a view in top plan of the cabochon gem grinder of FIG. 1;

FIG. 3 is a view in elevation, partly in section, and partly cut-awaytaken as indicated by the lines and arrows 3-3 which appear in FIG. 2;

FIG. 4 is a view in elevation taken as indicated by the lines and arrows4-4 which appear in FIG. 2;

FIG. 5 is a partial view in perspective of the template and gem holdingmechanism;

FIG. 6 is a partial view of the gem holding mechanism at about thebeginning of the grinding operation;

FIG. 7 is a partial view in elevation of the template mechanism taken asindicated by the lines and arrows 77 which appear in FIG. 2; and

FIG. 8 is a partial view in elevation of the gem grinding mechanismtaken as indicated by the lines and arrows 8-8 which appear in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the specificembodiment of the invention shown in the drawings, there is illustrateda gem grinder 11 which includes a support frame 13, brackets 15 mountedon frame 13 and supporting a pivot pin 17, an assembly plate 19 mountedon pivot pin 17, a mounting plate 21 connected to plate 19 by spacers23, and a mounting plate 25 connected to plate 21 by spacers 27.

An electric motor 29 has a shaft 31 and a gear 33 that meshes with gear35 on shaft 37. A spur gear 39 is mounted on the other end of shaft 37and meshes with a gear 41 mounted on worm gear shaft 43.

A worm 45 (FIGS. 2, 5 and 7) on shaft 43 meshes with gear 47 of shaft 49which is provided with a chuck or quill 51 that receives shaft 53 of atemplate 55 having a pattern 57 at the end of the shaft.

A worm 59 (FIGS. 2, 6 and 7) is also mounted on shaft 43 and meshes witha gear 61 on shaft 63 which is at right angles to shaft 43. Shaft 63 hasa quill or chuck 65 at one end which receives a dop or dop stick 67. Agem or stone 69 is glued to the end of the dop stick in position to beground to a smooth finish in a desired configuration which conforms tothe configuration of the pattern 57.

Motor 29 also drives another gear train which includes shaft 31, gear33, gear 35 and shaft 37. A worm 71 is mounted on shaft 37 and mesheswith a gear 73 on shaft 75 on which is mounted a worm gear 77 thatmeshes with a gear 79 on a shaft 81. A crank arm 83 I on shaft 81 drivesa connecting rod 85 that tilts rocker arm 87 which is mounted on ahollow shaft 89 that is rigidly connected to a housing 91 havingmounting plates 92 which support worm gear shaft 43. Housing 91 movesfrom its initial position, for example, 75 from the vertical, to thevertical, zero degree position, by means of the rotation of hollow shaft89.

Another motor 93 with a belt 94 drives a roller 95 mounted on supportbracket 97 on frame 13. A freely mounted roller 99 is also mounted onbracket 97, and the two rollers are adapted to support and rotate a drum101 having a cylindrical wall 103, a sidewall 105 that completelyencloses one side of the cylindrical wall 103, and an inner lip 107 thatprojects inwardly from the other side of wall 103.

A wear or a contact plate 109, which conforms to the shape and contoursof the inside of drum circumferential wall 103, is mounted on frame 13just below template 55.

In operation, the drum 101 is rotated by rollers 95 and 99 so as tomaintain a slurry of grinding grits or grains against the inside surfaceof cylindrical wall 103 by centrifugal force. The gem 69 to be ground tocabochon shape is positioned inside the drumlOl at an angle of about 75to the vertical'and grinding begins on an area of stone 69 which islocated at about 75 from the bottom of the stone. After this area isground to the desired shape, it touches the inner surface of the drumwall 103, and simultaneously the corresponding area on pattern 57 makescontact with wear or contact plate 109. Pattern 57 and contact plate 109are both made of electrically conductive material and are connected inan electrical circuit with a source of power and motor 29. The contactbetween pattern 57 and contact plate 109 acts as an electrical switch toclose the electrical circuit and energize motor 29. In other words, thepattern 57 and contact plate 109 sense that the stone area has beenground to the desired size and actuate motor 29 to rotate worms 4S and59 to rotate pattern 57 and stone 69. The stone is thereby rotated toanother high area which the grit slurry starts grinding to size, and thehigh area moves the pattern 57 away from contact plate 109, breakingelectrical contact, and stopping motor 29.

Also, the actuation of motor 29, in addition to rotating the pattern andgem, also actuates the gear train that moves housing 91 and shaft 49 todop stick 67 incrementally toward vertical position.

As the successive areas of stone 69 are ground to size, the rotation ofthe stone and the incremental movement toward the vertical cause eachsuccessive stone area to be ground to size in a substantially spiralpath on the stone, with ever decreasing spiral circumference.

It is to be noted that the stone 69 and pattern 57 are synchronized bymeans of identical worm and gear drives so as to move in identicalfashion. The shape of the pattern constitutes and provides a programwhich the stone follows in the course of the grinding.

The drum 101 is easily removable for the purpose of changing thecompound or for cleaning. Two drums are provided: the first drum is usedfor grinding the stone and washing, and the second drum may be used forpolishing, and may advantageously be made from a transparent syntheticplastic.

Cabochons made from grinding with the inventive machine may have anoval, rounded top with a flat bottorn for use in fingerrings. I 5

One of the important features of the invention is the internal lap ofthe stone within the drum 101 which permits grinding at less expensethan grinding with] the conventional diamond lap. The inventive machineis low in initial cost, and the grinding cost is lowdThe inventivemachine is especially suitable forhobbyists be- 7 highly polished, butnot faceted. It comes from the;

French word meaning cabbage or rounded head.

41 We claim: 1. A cabochon gemgrinding machinecomp'rising a drum havinga cylindrical wall and a lipsextending inwardly from the sides of thewall for retaining a slurry of abrasivematerial, means mounting the drum,so that its axis is horizontal and for rotating the drumtodistributeand maintain the slurry against the inner wallof the drum, dop means forholding a gem to be ground in contact with the slurry ata desired angleto the vertical to grind a desired area of the gem, and pattern meansconnected to the dop means for indicating the desired shape of the gem..

2. The gem grinder of claim 1 including means for ro-, tating the gemand the pattern means and for. moving' them toward a vertical positionto grind new areas of the gem.

3. The gem grinder of claim 1, wherein said means for rotating the drumincludes a drive roller and an idler roller which support the drumand'rotate it,

whereby said drum is easily removed for cleaning and easily replaced byother similar drums;

4. The gem grinder of claim 1, including sensing means for detectingwhen the gem area being ground has been ground to the desired pattern. 3

5. The gem grinder of claim 4 including actuatin means responsive tothesensing means for rotating the" axes of the pattern means andgem andfor moving said axis towardthe vertical to present another gem area to:

1. A cabochon gem grinding machine comprising a drum having acylindrical wall and a lip extending inwardly from the sides of the wallfor retaining a slurry of abrasive material, means mounting the drum sothat its axis is horizontal and for rotating the drum to distribute andmaintain the slurry against the inner wall of the drum, dop means forholding a gem to be ground in contact with the slurry at a desired angleto the vertical to grind a desired area of the gem, and pattern meansconnected to the dop means for indicating the desired shape of the gem.2. The gem grinder of claim 1 including means for rotating the gem andthe pattern means and for moving them toward a vertical position togrind new areas of the gem.
 3. The gem grinder of claim 1, wherein saidmeans for rotating the drum includes a drive roller and an idler rollerwhich support the drum and rotate it, whereby said drum is easilyremoved for cleaning and easily replaced by other similar drums.
 4. Thegem grinder of claim 1, including sensing means for detecting when thegem area being ground has been ground to the desired pattern.
 5. The gemgrinder of claim 4 including actuating means responsive to the sensingmeans for rotating the axes of the pattern means and gem and for movingsaid axis toward the vertical to present another gem area to be ground.